Our goal is to investigate the factors governing the decline of renal function in ADPKD, as well as responses to novel therapies in pre-clinical studies of specific small molecule inhibitor drugs as potential therapies for ADPKD. The hypothesis to be tested is that abnormal expression glycogen synthase kinase-3beta (GSKSbeta), a downstream effector of the Wnt/beta-catenin pathway, is central to ADPKD cyst expansion and that its specific inhibition will rescue the aberrant ADPKD phenotype in human ADPKD cell lines and reduce cystic expansion and decline in renal function in heterozygous polycystic kidney disease (PKD1) null mice. Aim 1: To determine the mechanism of action of GSK-3beta inhibition in human and mouse epithelial cells. Aim 2: To evaluate the therapeutic potential of GSK-3beta inhibitors in human ADPKD epithelial cells in vitro and in cystic heterozygous () PKD1 null mice in vivo. Cellular bioassays will include measurements of proliferation, adhesion, migration and protein polarization, and in vivo measurements will include longitudinal MRI imaging of cystic development and expansion, BUN and creatinine measurements, as well as kidney/heart weight, pathological and irrimunohistochemical examination of kidney tissues. We plan to use the most specific inhibitors reported to date, CHIR-73911 and CHIR-118637, which will be provided to us by Novartis (MTA executed). ADPKD cells will be treated with the inhibitors in culture and, along with vehicle-treated controls, will be subjected to adhesion and migration assays. ADPKD cells show increased adhesion and decreased migration, compared to normal renal epithelial cells. We predict that GSK-3beta inhibitors will ameliorate these defects. PKD1 mice will be treated for 6 weeks to 9 months with the inhibitors or vehicle starting at 2, 5 and 12 months of age, when cysts are known to develop. Cyst size will be measured via morphometry, and beta-catenin levels will be analyzed by Western blots. Completion of these studies will constitute pre-clinical testing of this class of compounds for ADPKD patients and will lead to a greater understanding of the molecular mechanisms underlying ADPKD progression. If the hypothesis is correct, these studies will form the basis for translation into a clinical trial of therapeutics for ADPKD. Research relevance: ADPKD is the most common, lethal, human genetic disease inherited as a dominant trait as a result of mutation in a single gene. With an estimated prevalence of 1:750, it affects 500,000 individuals in the United States. While rates of progression vary, 50% of ADPKD patients will develop endstage renal disease (ESRD). Our goal is to investigate the factors governing the decline of renal function in ADPKD, as well as responses to novel therapies in ADPKD cells and ADPKD mouse models.